It is conventional practice for quality control purposes to inspect fabric manufactured in textile mills.
At the present time, there are two basic techniques for such inspection. First, light is transmitted through the fabric and the intensity of the light measured. Variations in the intensity will indicate variations in density of the fabric material. Second, a reflective technique is employed wherein fabric is irradiated with light and the reflected light therefrom is analyzed.
Another technique known in the art for analyzing various materials is that of utilizing monochromatic light and developing diffraction patterns. For example, a single wire filament can be so analyzed as to size and form by irradiating the filaments with monochromatic light and analyzing the developed diffraction pattern. See, e.g., U.S. Pat. No. 3,659,950 issued May 2, 1972. However, so far as we are aware, no feasible technique has been developed prior to the present invention for a rapid analysis of fabric utilizing diffraction pattern techniques.